The success of portable computing this decade is due at least in part to the pioneering work of many companies in decades past.

Apple recently launched the iPad 2 to tremendous fanfare, and the device is being hailed as the latest and greatest portable computing device. Even though more powerful convertible tablet PCs were available years ago, the iPad has flourished thanks to its intuitive touch-based interface and a wealth of easy-to-install third-party applications. Apple sold around 15 million iPads in 2010, and the company looks poised to have a big year with the iPad 2.

Important milestones in portable computing include devices such as single-chip calculators, 'laptops' that weighed more than 10kg, digital organisers and even a few older Apple inventions. Here's a look at 18 of the most notable mobile computers.

1971: Busicom LE-120A 'Handy-LE' Calculator

Milestone: First pocket-size calculator

Legacy: It might seem strange to kick off a list of portable computing milestones with a calculator, but this little machine from Busicom was one of the first handheld devices that could carry out a computing function. So-called handheld calculators existed before this product, but the Handy-LE was truly the first calculator you could easily hold in your hand or fit in your pocket. The Handy-LE's small size was due to the single-chip calculator circuit - the Mostek MK610 - that carried out the device's computing functions.

Photo: Courtesy of Dentaku Museum

1978: Parker Bros Merlin Computer Toy

Milestone: Early mass-market computer toy

Legacy: It may have been a toy, but the Parker Bros Merlin was one of the earliest portable computers that many children growing up in the late 70s and early 80s encountered. The device had a simple microprocessor and could play six different games: Tic-Tac-Toe, Echo, Blackjack, Magic Square, Mindbender and Music Machine. The last game provided the device with limited programmability, allowing you to input up to 48 tones and rests and have the computer play back your composition.

Photo: Courtesy of Retroland

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  1. Groundbreaking portable devices
  2. Osborne 1 Portable Computer
  3. TRS-80 Model 100 Portable PC
  4. Psion Series 3 Minicomputer
  5. Panasonic Toughbook CF-25 Laptop
  6. Acer TravelMate
  7. Samsung Q1
  8. Apple iPhone
  9. Apple iPad